This invention relates to protective coatings on decorative compositions and, more specifically, for formulas that facilitate the application thereof. For convenience, the words xe2x80x9cclear coating(s)xe2x80x9d will be frequently used herein as a generic term for components that are essentially water-white. This invention is particularly concerned with colorants that may temporarily impart color to these otherwise clear coatings, the color dissipating over a relatively short period of time. A further aspect of the invention is a method of designing the concentration of colorant such that the opacity is minimal, thus making it possible to utilize the translucent feature to judge the film thickness.
The function of a clear coating is that, when uniformly applied, it improves the service life and protection afforded by the coating system. Modern high performance coatings are often chosen based upon their ability to maintain their color and gloss over long periods. It has been an aim of manufacturers to achieve more permanency and fastness of color to resist fading for as long as possible. Clear coatings, especially those that are resistant to UV light deterioration, have been found to be highly effective in providing a means to this goal. Clear coatings can be formulated such that they improve the color stability and gloss retention of a base coat and reduce the tendency of color pigments, associated with these base coats, to fade in sunlight. However, to be effective, they must be applied uniformly.
In the past, applying a clear coat at a uniform film thickness over a previously coated surface, especially one that has a high gloss, has been a problem. The applicator has difficulty with the control of the uniformity of wet film thickness since it is difficult to observe the amount of coating that has been applied. Such a limitation is a serious problem, since the amount of protection which the clear coating provides to the underlying base coat (a pigmented coating) is affected by the thickness of the clear coat. If the clear coat is applied at a film thickness that is less than the designed minimum, the resistance to ultra-violet (UV) light transmission through the clear coat is compromised, and the coating""s function is compromised. The result is an undesirable variation in color uniformity observed after a period of time.
For the foregoing reasons, there is a need for a paint additive that allows an applicator to judge the thickness of a clear coating film that is being applied to a substrate.
Protective clear coatings can be applied over colored base coats in order to protect the pigmented base coats from deterioration by UV light. It is important that film thickness be uniform. The present invention is directed to a chemical composition that satisfies the need for a paint additive that aids the applicator in determining that the coating film is being applied at the correct film thickness and uniformity.
This discovery involves a chemical composition comprising a color-dissipatable dye that is unstable when exposed to UV light. The exposure to sunlight (either direct or diffuse) of this novel combination of clear coating and color-dissipatable dye results in the color being dissipated by photo chemical or thermal, oxidation and/or reduction. When mixed with the coating at the proper concentration, the result is a coating that provides a translucent color that has limited opacity and thus reveals thin versus thick film build. Because the colorant dissipates, the return to the xe2x80x9cclear coatingxe2x80x9d appearance takes place within a reasonable timeframe, preferably from hours to a few days in a typical formula composition.
An embodiment of this invention is a composition comprising a color-dissipatable dye preferably one selected from a group of dyes including basonyl green, basonyl blue, pylam blue, trialmethanes; flexo yellow, diarylmethane; FDandC #2 indigotene; FDandC #2 lake; FDandC #1, FDandC #3 green, triphenylmethanes; FDandC #1 lake; FDandC #5 yellow, erythrosine lake; and FDandC #5 yellow lake.
The preferred application of this technology is realized in the form of a dissipating colorant being introduced into an otherwise clear coating, where the polymeric composition of the clear coating is selected from a group including acrylic, urethane, epoxy, or polyester. In all of these polymeric options, the product can be delivered in either waterborne, solvent, or 100% solids (i.e. solvent-free) form.
Another embodiment of this technology involves a color-dissipating coating composition that incorporates a compatibilizer carrier solution selected to increase the ease of measuring the dye for addition to the clear coating composition, to which is added a light-unstable dye. The dye mixture is further selected to facilitate the tolerance of the dye when mixed into the clear coating composition. The dye carrier is selected from a group including water, glycerin, propylene glycol, sodium benzoate, hydroxyl propyl methylcellulose, aromatic, aliphatic and oxygenated solvents.
An objective of this invention is to provide a method of making an xe2x80x9capplicator-friendlyxe2x80x9d clear coating that exhibits a translucent coloring, said color permitting the visual detection of uniform application, said color dissipating over a relatively short period of time when exposed to one or more of the dissipation-promoting conditions of photochemical or thermal, oxidation and/or reduction, depending on the chemical composition of the dye. A second objective is to provide a practical and highly reliable mechanism for delivering a uniform protective film, which will subsequently protect a substrate from deterioration caused by weathering. A third objective is to describe the techniques to be used to obtain a composition having color sufficient to obtain the desired color contrast, such that the coating provides the performance objectives. A fourth objective is to describe techniques for incorporating the colorants into clear coating formulae that are routinely used in this service.
Another objective of this disclosure is to define the method of applying a protective coating having enough color strength that an applicator is provided with a means for easily determining where said coating has been applied, which encompasses the lifetime requirements for the color-dissipating dye component incorporated in said composition previously described, whereupon color of the light-unstable dye will have proceeded to disappear.
Another objective of this invention is to provide a method which provides a means for avoiding skips and thin spots (holidays) in a freshly applied clear coating and which also provides a means for accenting sags and runs in an applied clear coat by means of the color contrast which exists between the desired film thickness and a high film thickness associated with such sags and runs.
These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.